The present invention relates generally to inkjet printheads, and more particularly to generation of fire signals for controlling ejection of ink drops from printheads.
A conventional inkjet printing system includes a printhead, an ink supply which supplies liquid ink to the printhead, and an electronic controller which controls the printhead. The printhead ejects ink drops through a plurality of orifices or nozzles and toward a print medium, such as a sheet of paper, so as to print onto the print medium. Typically, the orifices are arranged in one or more arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other.
Typically, the printhead ejects the ink drops through the nozzles by rapidly heating a small volume of ink located in vaporization chambers with small electric heaters, such as thin film resisters. Heating the ink causes the ink to vaporize and be ejected from the nozzles. Typically, for one dot of ink, a remote printhead controller typically located as part of the processing electronics of a printer, controls the timing and activation of an electrical current from a power supply external to the printhead with a fire pulse. The electrical current is passed through a selected thin film resister to heat the ink in a corresponding selected vaporization chamber.
In one type of inkjet printing system, printheads receive fire signals containing fire pulses from the electronic controller. In one arrangement, the fire signal is fed directly to the nozzles in the printhead. In another arrangement, the fire signal is latched in the printhead, and the latched version of the fire signal is fed to the nozzles to control the ejection of ink drops from the nozzles.
In either of the above two arrangements, the electronic controller of the printer maintains control of all timing related to the fire signal. The timing related to the fire signal primarily refers to the actual width of the fire pulse and the point in time at which the fire pulse occurs. The electronic controller controlling the timing related to the fire signal works well for printheads capable of printing only a single column at a time, because such printheads only need one fire signal to the printhead to control the ejection of ink drops from the printhead.
One proposed printhead has the capability of printing multiple columns of the same color or multiple columns of different colors simultaneously.
In one arrangement, commonly referred to as a wide-array inkjet printing system, a plurality of individual printheads, also referred to as printhead dies, are mounted on a single carrier. In one proposed arrangement, a wide-array inkjet printing system includes printheads which have the capability of printing multiple columns of the same color or multiple columns of different colors simultaneously. In any of these arrangements, a number of nozzles and, therefore, an overall number of ink drops which can be ejected per second is increased. Since the overall number of drops which can be ejected per second is increased, printing speed can be increased with a wide-array inkjet printing system and/or printheads having the capability of printing multiple columns simultaneously.
The energy requirements of different printheads and/or different print columns can possibly require a different fire pulse width for each printhead and/or print column due to processing/manufacturing variability. In this case, the number of fire signals necessary for the inkjet printing system increases significantly. For example, a 4-color integrated printhead requires four fire signals in order to independently control each color. If six of the example 4-color integrated printheads are disposed on a single carrier to form a print bar array in a wide-array inkjet printing system, the number of required fire signals increases to 24.
For reasons stated above and for other reasons presented in greater detail in the Description of the Preferred Embodiment section of the present specification, a wide-array inkjet printing system and/or a printhead having the capability of printing multiple columns is desired which minimizes the number of fire signals provided from the electronic controller to the printhead(s).
One aspect of the present invention provides an inkjet printhead including nozzles, firing resisters, and fire pulse generator circuitry. The fire pulse generator circuitry is responsive to a start fire signal to generate a plurality of fire signals. Each fire signal has a series of fire pulses, and the fire pulse generator circuitry generates the fire signals by controlling the initiation and duration of the fire pulses. The fire pulses control timing and activation of electrical current through the firing resisters to thereby control ejection of ink drops from the nozzles.
In one embodiment, the fire pulse generator circuitry includes counters. Each counter is responsive to the initiation of a corresponding fire pulse to count to a corresponding count value representing the duration of the corresponding fire pulse. In one embodiment, the fire pulse generator circuitry further includes pulse width registers for holding pulse width values. The counters are each preloaded with a corresponding pulse width value and respond to the initiation of the corresponding fire pulse to count down from the corresponding pulse width value to determine the duration of the corresponding fire pulse. In one embodiment, the fire pulse generator circuitry includes controllers controlling corresponding counters. Each controller provides a corresponding fire pulse and activates a start signal to the corresponding counter to initiate the count. Each counter activates a stop signal to the corresponding controller to terminate the corresponding fire pulse when the count value is reached.
In one embodiment, the fire pulse generator circuitry includes a start fire detection circuit receiving the start fire signal and verifying that a valid active start fire signal is received. In one embodiment, the start fire detection circuit receives a clock signal having active transitions and verifies that the valid active start fire signal is received by requiring that the active start fire signal is present for at least two of the active transitions of the clock signal.
In one embodiment, an active start fire signal is provided to the fire pulse generator circuitry each time a fire pulse is generated. In another embodiment, an active start fire signal is provided to the fire pulse generator circuitry only at the beginning of a print swath.
In one embodiment, the fire pulse generator circuitry also controls dead-time between fire pulses in the series of fire pulses in each fire signal. In one embodiment, the fire pulse generator circuitry includes dead-time counters. Each dead-time counter is responsive to a termination of a corresponding fire pulse to count to a corresponding dead-time count value representing the duration of the dead-time between fire pulses. In one embodiment, the fire pulse generator circuitry further includes dead-time registers for holding dead-time values. The dead-time counters are each preloaded with a corresponding dead-time value and respond to the termination of the corresponding fire pulse to count down from the corresponding dead-time value to determine the dead-time between fire pulses.
One aspect of the present invention provides an inkjet printhead assembly including at least one printhead. Each printhead includes nozzles and firing resisters. The inkjet printhead assembly includes fire pulse generator circuitry responsive to a first start fire signal to generate a plurality of fire signals. Each fire signal has a series of fire pulses, and the fire pulse generator circuitry generates the fire signals by controlling the initiation and duration of the fire pulses. The fire pulses control timing and activation of electrical current through the firing resisters to thereby control ejection of ink drops from the nozzles.
In one embodiment, the first start fire signal is provided from a printer controller located external from the inkjet printhead assembly. In one embodiment, the inkjet printhead assembly includes a carrier, N printheads disposed on the carrier, and a module manager disposed on the carrier. In one embodiment, the module manager receives a second start fire signal from a printer controller located external from the inkjet printhead assembly and provides the first start fire signal representing the first start signal to each of the N printheads.
One aspect of the present invention provides an inkjet printhead assembly including, a carrier, N printheads disposed on the carrier, and a module manager disposed on the carrier. Each printhead includes nozzles and firing resisters. The module manager includes fire pulse generator circuitry responsive to a start fire signal to generate a plurality of fire signals. Each fire signal has a series of fire pulses, and the fire pulse generator circuitry generates the fire signals by controlling the initiation and duration of the fire pulses. The fire pulses control timing and activation of electrical current through the firing resisters to thereby control ejection of ink drops from the nozzles of the printheads.
One aspect of the present invention provides an inkjet printing system including a printer controller providing a start fire signal. The inkjet printing system includes an inkjet printhead assembly having at least one printhead and fire pulse generator circuitry. Each printhead includes nozzles and firing resisters. The fire pulse generator circuitry is responsive to the start fire signal to generate a plurality of fire signals. Each fire signal has a series of fire pulses, and the fire pulse generator circuitry generates the fire signals by controlling the initiation and duration of the fire pulses. The fire pulses control timing and activation of electrical current through the firing resisters to thereby control ejection of ink drops from the nozzles.
One aspect of the present invention provides a method of inkjet printing including receiving a start fire signal at a printhead assembly, which includes at least one printhead having nozzles and firing resisters. The method includes generating, in response to the start fire signal, a plurality of fire signals, each having a series of fire pulses, by controlling the initiation and duration of the fire pulses internal to the printhead assembly. The method includes controlling timing and activation of electrical current through the firing resisters to thereby control ejection of ink drops from the nozzles based on the fire pulses.
An inkjet printhead/printhead assembly according to the present invention can provide different fire pulse widths for different printheads and/or print columns to accommodate the energy requirements of different printheads and/or different print columns resulting from processing/manufacturing variability without increasing the number of fire signals from the printer controller to the printhead/printhead assembly. One embodiment of the fire pulse generator circuitry according to the present invention only requires one start fire conductor between the printer controller and the printhead/printhead assembly.
Thus, the printhead/printhead assembly containing fire pulse generator circuitry according to the present invention can significantly reduce the following: the number of fire signal conductive paths to and from the printhead/printhead assembly; the number of drivers in the electronic controller necessary to transmit the fire signals from the electronic controller to the printhead assembly; and the number of pads required on the printhead/printhead assembly to receive the fire signals. Furthermore, in one embodiment having multiple printheads disposed on a carrier to form a printhead assembly and having the fire pulse generator circuitry internal to the printheads, the wiring complexity of the carrier is reduced.